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T9-T12 Vertebrae

vertebrae thoracicae IX-XII

The lower four thoracic vertebrae transition toward the lumbar region, with T9 through T12 articulating with the corresponding ribs, T11 and T12 with floating ribs, and providing origin for parts of the diaphragm and abdominal muscles.

Anatomical Data

Structure & Landmarks

Articulations
  • Adjacent vertebrae
  • Bilateral ribs (T11 and T12 floating)
  • Bilateral facet joints
Landmarks
  • Transitional body shape between thoracic and lumbar
  • Mamillary and accessory processes beginning to appear
OssificationAs per thoracic vertebra pattern.
Clinical Relevance

Clinical Notes

The lower thoracic vertebrae T9 through T12 represent the transition zone where the thoracic cage ends and the mobile thoracolumbar junction begins. T11 and T12 have floating ribs (not connected anteriorly). The thoracolumbar junction at T12-L1 is the most common site of major spinal column injury because the rigid thoracic spine meets the mobile lumbar spine, creating a stress riser that fractures preferentially at this level in high-energy trauma.

Pathology

Common Injuries & Conditions

Thoracolumbar Burst Fracture

The T11-L2 junction is the most common site of spinal fracture after falls and vehicle collisions; burst fractures can push bone fragments into the canal.

Chance Fracture

A flexion-distraction fracture through the vertebral body and posterior elements, classically from a lap belt, often associated with abdominal visceral injury.

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